The present disclosure describes a method and an apparatus for detecting particles in a gas by condensing vapor on the particles to form droplets, which are then detected by an optical, light-scattering detector. Instruments using vapor condensation on particles to form droplets for detection are referred to as condensation particle counters (CPC), or as condensation nucleus counters (CNC). A variety of working fluids can be used to generate vapor for condensation. The most common working fluids are butyl alcohol and water.
Condensation particle counters are useful in many applications. In air pollution and climate research, for instance, the instrument is often used with an electrical mobility analyzer to determine the concentration and size distribution of particles in the ambient atmosphere. The instrument can also be used to detect particulate contaminants suspended in clean-room air for clean-room monitoring and contamination control purposes. In addition, CPC is widely used in laboratory research to study the property and behavior of small airborne particles.
The most important process in a CPC is the process of vapor generation, condensation and droplet growth. The present disclosure describes a new approach to creating super-saturation for vapor condensation and droplet growth, leading to a compact measuring device with improved performance characteristics.